The present disclosure relates generally to electrodeless high intensity discharge (HID) lamps. More particularly, this disclosure relates to a ceramic induction HID system and different methods and apparatus for positioning and holding a ceramic discharge chamber inside an induction coil.
HID lighting was initially developed in the 1960's and such lighting provides approximately twenty percent (20%) of all artificial light. The electrodeless HID lamps provide a unique combination of high efficacy, high brightness, high wattage, long life, and good color. Presently, induction HID systems rely on a positioning member to hold a discharge vessel or arc body at a prescribed location relative to and within an annular induction coil. Such a construction is highly susceptible to mechanical motion which adversely results in a change in the coupling between the coil and the arc body, mostly compromising coupling efficiency and consequently decreasing efficacy of the system. Further, known positioning members are typically connected to the coil in a manner that blocks a significant amount of usable light.
Whereas quartz arc bodies have been used in the past, a ceramic arc body presents different challenges. Improved resistance to dose loss, and the ability to operate at higher temperatures in an efficient manner are just a few reasons to use a ceramic material for the arc body. Particularly, the ceramic arc body can operate at higher temperatures but is also prone to cracking if it experiences a large thermal gradient such as by contact with a material with a substantially different temperature. It is important that the ceramic arc body not be permitted to engage the coil because the differences in temperature of the two materials will lead to cracking of the ceramic. Optimal operation of the electrodeless ceramic HID lamp also requires precise location between the arc body and the surrounding coil. Thus, there are competing concerns of accurately and precisely locating the arc body within the coil, addressing thermal issues, and maximizing the amount of light output from the assembly, i.e., not unduly blocking large portions of the light output.
However, alternative ways to precisely locate the ceramic arc body within the induction coil, and for limiting the potential for high temperature gradients as a result of using materials having different thermal coefficients, which leads to cracking and leakage of the dose, are required.